Packaging container, packaging method and packing apparatus using same

ABSTRACT

For providing a packaging container which permits easy separation of a film from the container, as well as a packaging method and a packing apparatus using the packaging container, the packaging container is constituted by a container for accommodating an article to be packaged, the container having a peripheral fitting edge and an upper opening, and a cover member formed by a film for covering the opening of the container, end portions of the film being converged to form a solid edge portion for fitting with the fitting edge of the container.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a packaging container having anupper opening such as a tray or a cup for receiving therein an articleto be packaged and covering the upper opening with film, as well as apackaging method and packing apparatus using the container.

[0003] 2. Description of the Prior Art

[0004] Heretofore, as one of packaging methods of this type used mostfrequently there has been known a stretch packaging method. According tothis known method, a container having an upper opening is charged withan article to be packaged and is then covered from above with asynthetic resin film such as a soft polyvinyl chloride film or apolyethylene film while stretching the film up to the bottom of thecontainer until the stretched film portions overlap each other, then theoverlapped portions are united by utilizing the tackiness of the filmitself or both tackiness and heat-fusibility of the film.

[0005] This packaging method is highly versatile for the difference insize and shape of containers and permits packaging even when an articleto be packaged projects upward from the container used. Besides, sincethe whole of the container charged with an article to be packaged iswrapped in a single film, this packaging method does not depend on thematerial of the container used. However, since the film must be foldedback up to the container bottom and overlapped, the amount of the filmused is large, thus leading to the discharge of a large amount ofwastes. There also arise such problems as the film is apt to tear andthe package is difficult to be opened.

[0006] For eliminating such drawbacks involved in the stretch packagingmethod there has been invented such a method as is disclosed in JapanesePublished Examined Patent Application No. Sho 57-29335. FIG. 19 is asectional view showing a container about to be sealed by the method andFIG. 20 is a sectional view of the container after sealed. According tothe method, a container 1 having an upper opening is formed with an edgeportion 2 which projects laterally outwards, and in a charged state ofthe container 1 with an article 3 to be packaged, the container 1 iscovered with film 4 which has been cut to an area larger than the areaof the upper opening, as shown in FIG. 19, then the whole of the film 4is heated by subjecting the film to infrared heating or by blowing hotair to the film, while pressing the overhanging portions of the filmoverhanging from the edge portion 2 against side faces of the container1, allowing the film 4 to shrink thermally, and at the same time thefilm is heat-fused to the underside of the edge portion 2 to seal theto-be-packaged article 3 as in FIG. 20.

[0007] Problem involved in such conventional technique will now bedescribed. The packaging method disclosed in the foregoing JapanesePublished Examined Patent Application No. Sho 57-29335 involves aproblem that it is difficult to strip off the film 4 alone at the timeof opening the package. More particularly, the heat-fused portionbetween the film 4 and the container 1 is so strong that the containeroften tears at the time of stripping off the film. Therefore, forretaining the container 1 in its original state it is necessary toremove the heat-fused portion of the film 4 with use of an edged toolsuch as a knife. A further difficulty is encountered in the case wherethe to-be-packaged article 3 projects higher than the height of thecontainer 1.

SUMMARY OF THE INVENTION

[0008] It is an object of the invention to provide a packagingcontainer, a packaging method and a packing apparatus using thecontainer, which permit film to be separated easily from the container.

[0009] For solving the above-mentioned problems, according to thepresent invention, in one aspect thereof, there is provided a packagingcontainer comprising a container for accommodating an article to bepackaged, the container having a peripheral fitting edge and an upperopening and a cover member formed by a film for covering the opening ofthe container, end portions of the film being converged to form a solidedge portion for fitting with the fitting edge of the container.

[0010] Another aspect of the present invention there is provided apackaging method wherein an opening of a container for accommodating anarticle to be packaged is covered with a film of a size which permitsthe film to overhang sideways from the opening of the container, andoverhanging portions of the film overhanging sideways from the containeropening are converged to form a solid edge portion of a high rigidityfor fitting with a fitting edge formed on the container side.

[0011] Another aspect of the present invention there is provided apackaging method wherein a central portion of a film for covering anopening of a container which accommodates an article to be packaged isstretched outwards of the film so as to afford a film size overhangingsideways from the container opening, then the container opening iscovered with the thus-stretched film, and overhanging portions of thefilm overhanging from the container opening are converged to form asolid edge portion for fitting with a fitting edge formed on thecontainer side, the solid edge portion having a higher rigidity than therigidity of the film.

[0012] Further aspect of the present invention there is provided apackaging apparatus comprising a controller for controlling each portionso as to allow execution of certain operation, a film grippers,controlled by the controller, for grasping a film afforded a film sizeoverhanging sideways from the opening of the container whichaccommodates an article to be packaged, the film grippers positioningthe film above the container opening, a mechanism, controlled by thecontroller, for moving the film grasped by the film grippers to thecontainer opening relatively so as to cover the container opening withthe film, and a mechanism, controlled by the controller, for convergingthe overhanging portions of the film overhanging sideways from thecontainer opening to form a solid edge portion of a high rigidity forfitting with a fitting edge formed on the container side.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A more complete appreciation of the present invention and many ofthe attendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, in which:

[0014]FIG. 1 is a perspective view of a packaging apparatus according tothe first embodiment of the present invention;

[0015]FIG. 2 is a front view of a container with film drawn out abovethe container;

[0016]FIG. 3 is a front view of the container with film positioned onthe container;

[0017]FIG. 4 is a front view of the container with film portionsoverhanging from the container pulled down sideways of the container;

[0018]FIG. 5 is a perspective view of the container with film positionedon the container;

[0019]FIG. 6 is a perspective view of the container with film positionedon the container and spread;

[0020]FIG. 7 is a front view of the container with film started toconverge under the jet of hot air;

[0021]FIG. 8 is a front view of the container with a solid edge portionformed by film;

[0022]FIG. 9 is a perspective view of a packaging apparatus according tothe second embodiment of the present invention;

[0023]FIG. 10 is a perspective view showing an inner structure of thepacking apparatus;

[0024]FIG. 11 is a perspective view showing another example of an innerstructure of the packing apparatus;

[0025]FIG. 12 is a perspective view of a packaging apparatus accordingto the third embodiment of the present invention.

[0026]FIG. 13 is a perspective of an inner structure of a packaging unitwith film being subjected to pre-stretching in the third embodiment;

[0027]FIG. 14 is a perspective view of the inner structure of thepackaging unit showing a film stretching mechanism in descent positionfor film stretching;

[0028]FIG. 15 is a perspective view of the inner structure of thepackaging unit showing a state in which the film stretching mechanismstretches the film in the third embodiment;

[0029]FIG. 16 is a perspective view of the inner structure of thepackaging unit showing a state in which hot air is blown against filmends by means of blowers in the third embodiment;

[0030]FIG. 17 is a block diagram showing an operating mechanism;

[0031]FIG. 18 is a flow chart showing an operating process;

[0032]FIG. 19 is a partially cut-away front view of a container withfilm applied over the container, showing a conventional example; and

[0033]FIG. 20 is a partially cut-away front view in a fused state offilm.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] The present invention relates to a packaging container having anupper opening such as a tray or a cup for receiving therein an articleto be packaged and covering the upper opening with film, as well as apackaging method and packing apparatus using the container. Thus, somepreferred embodiments are of the packing container, the packing methodand the packing apparatus is introduced hereinafter.

[0035] Since one embodiment of the present invention resides in apackaging container comprising a container for accommodating an articleto be packaged, the container having a peripheral fitting edge and anupper opening, and a cover member formed by a film for covering theopening of the container, end portions of the film being converged toform a solid edge portion for fitting with the fitting edge of thecontainer. Therefore, when the packaged article is to be taken out, bymerely putting a finger on the solid edge portion and removing the solidedge portion from the fitting edge of the container, the film can beseparated easily from the container and thus the upper surface of thecontainer in a packaged state can be opened easily without damaging thecontainer.

[0036] Another embodiment of the present invention resides in apackaging container wherein the fitting edge of the container is formedso as to project laterally outwards. Therefore, the solid edge portionof the film can be positively fitted with the container and it ispossible to enhance the sealing performance.

[0037] Another embodiment of the present invention resides in apackaging container wherein the opening of the container is formed in ashape which expands upwards of the container, and the edge of thecontainer opening is formed as the fitting edge. Therefore, even withoutforming an outwardly projecting edge-like portion on the container side,the solid edge portion of the film can be fitted with the containerpositively.

[0038] Another embodiment of the present invention resides in apackaging container wherein the film is a stretch film. Therefore, evenan article to be packaged which projects upwards of the container can bepackaged positively.

[0039] One embodiment of the present invention resides in a packagingmethod wherein an opening of a container for accommodating an article tobe packaged is covered with a film of a size which permits the film tooverhang sideways from the opening of the container, and overhangingportions of the film overhanging sideways from the container opening areconverged to form a solid edge portion of a high rigidity for fittingwith a fitting edge formed on the container side. Therefore, thecontainer can be packaged with the film in an extremely simple workingprocess.

[0040] Other embodiment of the present invention resides in a packagingmethod wherein a central portion of a film for covering an opening of acontainer which accommodates an article to be packaged is stretchedoutwards of the film so as to afford a film size overhanging sidewaysfrom the container opening, then the container opening is covered withthe thus-stretched film, and overhanging portions of the filmoverhanging from the container opening are converged to form a solidedge portion for fitting with a fitting edge formed on the containerside, the solid edge portion having a higher rigidity than the rigidityof the film. Therefore, the container can be packaged with the film inan extremely simple working process. There also is attained an effectthat the formation of the solid edge portion is ensured because the filmis stretched uniformly along the container edge. That the film isstretched uniformly brings about a further effect that not onlywrinkling of the film caused by a returning force in the containeropening at the time of formation of a packaged container is suppressedbut also the deformation of the container is prevented.

[0041] Another embodiment of the present invention resides in apackaging method wherein the central portion of the film is stretchedoutwards of the film and in directions perpendicular to sides of thecontainer. Therefore, the film can be stretched in conformity with theshape of the container used. Also, there is attained an effect that theformation of the solid edge portion is ensured because the film isstretched uniformly along the container edge. That the film is stretcheduniformly brings about a further effect that not only wrinkling of thefilm caused by a returning force in the container opening at the time offormation of a packaged container is suppressed but also the deformationof the container is prevented.

[0042] Another embodiment of the present invention resides in apackaging method wherein a central portion of the film is allowed tostretch outwards of the film by straight movement of film grippers thatgrasps the film. Therefore, it is possible to reduce the necessaryoperating steps and necessary parts for apparatus because the film canbe stretched by use of the film grippers that is required instinctivelyfor grasping the film.

[0043] Another embodiment of the present invention resides in apackaging method wherein a central portion of the film is allowed tostretch outwards of the film by rotating movement of film grippers thatgrasps the film. Therefore, it is possible to reduce the necessaryoperating steps and necessary parts for apparatus because the film canbe stretched by use of the film grippers that is required instinctivelyfor grasping the film.

[0044] Another embodiment of the present invention resides in apackaging method wherein a central portion of the film is allowed tostretch outwards of the film by the steps including grasping the film bya film gripper, sinking a plurality of fingers that is capable ofspreading, and spreading the fingers so as to stretch outwards of thefilm. Therefore, there is attained an effect that the formation of thesolid edge portion is ensured. There is attained a further effect thatnot only wrinkling of the film caused by a returning force in thecontainer opening at the time of formation of a packaged container issuppressed but also the deformation of the container is prevented.

[0045] Another embodiment of the present invention resides in apackaging method wherein end portions of the film are allowed toconverge by heating to form the solid edge portion. Therefore, the solidedge portion can be formed easily.

[0046] One embodiment of the present invention resides in a packagingapparatus comprising a controller for controlling each portion so as toallow execution of certain operation, a film grippers, controlled by thecontroller, for grasping a film afforded a film size overhangingsideways from the opening of the container which accommodates an articleto be packaged, the film grippers positioning the film above thecontainer opening, a mechanism, controlled by the controller, for movingthe film grasped by the film grippers to the container openingrelatively so as to cover the container opening with the film, and amechanism, controlled by the controller, for converging the overhangingportions of the film overhanging sideways from the container opening toform a solid edge portion of a high rigidity for fitting with a fittingedge formed on the container side. Therefore, the container can bepackaged with the film in an extremely simple working process.

[0047] Another embodiment of the present invention resides in apackaging apparatus wherein the film grippers grasp four corners of thefilm and stretch the film outwards of the film. Therefore, the containercan be packaged with the film in an extremely simple working process.There also is attained an effect that the formation of the solid edgeportion is ensured because the film is stretched uniformly along thecontainer edge. That the film is stretched uniformly brings about afurther effect that not only wrinkling of the film caused by a returningforce in the container opening at the time of formation of a packagedcontainer is suppressed but also the deformation of the container isprevented.

[0048] Another embodiment of the present invention resides in apackaging apparatus further comprising a film pulling mechanism,controlled by the controller, that grasps each sides between the cornersof the film and stretch the film outwards of the film. Therefore, thefilm can be stretched in conformity with the shape of the containerused. Also, there is attained an effect that the formation of the solidedge portion is ensured because the film is stretched uniformly alongthe container edge. That the film is stretched uniformly brings about afurther effect that not only wrinkling of the film caused by a returningforce in the container opening at the time of formation of a packagedcontainer is suppressed but also the deformation of the container isprevented. Further, it is possible to reduce the necessary operatingsteps and necessary parts for apparatus because the film can bestretched by use of the film grippers that is required instinctively forgrasping the film.

[0049] Another embodiment of the present invention resides in apackaging apparatus further comprising a plurality of fingers,controlled by the controller, that is capable of spreading and spread soas to stretch outwards of the film. Therefore, there is attained aneffect that the formation of the solid edge portion is ensured. There isattained a further effect that not only wrinkling of the film caused bya returning force in the container opening at the time of formation of apackaged container is suppressed but also the deformation of thecontainer is prevented.

[0050] Another embodiment of the present invention resides in apackaging apparatus wherein the mechanism for converging the filmconverges by heating the edge of the film to form the solid edgeportion. Therefore, the solid edge portion can be formed easily.

[0051] Another embodiment of the present invention resides in apackaging apparatus further comprising a film unit for cutting the filmso as to afford a film size overhanging sideways from the opening of thecontainer. Therefore, appropriate size film for the container can besupplied automatically, so that operation is improved.

First Embodiment

[0052] An embodiment of the present invention will be described belowwith reference to FIGS. 1 to 8. What is illustrated in FIG. 1 is apackaging apparatus 5. The packaging apparatus 5 comprises a packagingunit 6, a container feed unit 7 and a container discharge unit 8disposed on the left and right sides, respectively, of the packagingunit 6, and a film loading unit 9 disposed behind the packaging unit 6.With this arrangement, the packaging apparatus 5 can packagecontinuously a large number of articles to be packaged. The containerfeed unit 7 feeds a container 10 to the packaging unit 6 in a continuousmanner, the container discharge unit 8 discharges the container 10 afterpackaged, and the film loading unit 9 feeds a film 11 to the packagingunit 6 in a successive manner. As to detailed structures of thecontainer feed unit 7, container discharge unit 8 and film loading unit9, explanations thereof are here omitted.

[0053] The packaging unit 6 is provided with a container carrier 12 onwhich the container 10 is placed. Four blowers 13 are arranged so as tosurround four sides of the container 10 put on the container carrier 12.Also mounted are four film grippers 14 (only two are shown in FIG. 1)for gripping four corners of the film 11 pulled out from the filmloading unit 9.

[0054] The container 10 is formed with an upper opening 16 having aperipheral fitting edge 15 and is in the shape of an upwardly expandedtray as a whole.

[0055] In such a construction, as shown in FIG. 2, the container 10charged with an article (not shown) to be packaged is fed from thecontainer feed unit 7 onto the container carrier 12 in the packagingunit 6 and at the same time the film 11 is fed from the film loadingunit 9. The film 11 has been cut and is gripped at four corners thereofby the film grippers 14. In this state, the film grippers 14 move downinto contact with the container 10 while pulling the film so as not towrinkle the film, to cover the opening 16 of the container 10, as shownin FIGS. 3, 5 and 6. Further, as shown in FIG. 4, the film grippers 14turn and move down, causing overhanging portions of the film 11overhanging from the container 10 to approach the side faces of thecontainer. At this time it is desirable that the gripping direction ofthe film grippers 14 is an upward direction toward the fitting edge 15.

[0056] When end portions of the film 11 have reached a position lowerthan the opening 16 of the container 10 in a fully pulled state of thefilm 11, the blowers 13 positioned around the container 10 are driven toblow hot air against the four sides of the container. Taking theinfluence on the article to be packaged into account, a jet of hot airat 120° C. for about 3 seconds is desirable. With this hot air, endportions of the film 11 become hot and shrink. As a result of thisthermal shrinkage the overhanging portions of the film 11 overhangingfrom the container 10 converge to enhance their rigidity and extendinside along the fitting edge 15 to form a solid edge portion 17 belowthe fitting edge 15. In this case, an appropriate timing for ungrippingthe film 11 from the gripped state by the film grippers 14 is set insynchronism with shrinkage of the film positioned at the side portionsof the container 10. The solid edge portion 17 is formed also by thefour corners of the film 11. As a result of formation of the solid edgeportion 17 there is formed a cover member 18 by the film 11. The solidedge portion 17 is fitted with the fitting edge 15 of the container 10and is not heat-fused to the container. Of course, the solid edgeportion 17 may be heat-fused to the container 10 to such an extent thatit can be stripped off easily. Therefore, when the article thus packagedis to be taken out from the container 10, a finger is put on the solidedge portion 17 and is moved in a direction to come off the fitting edge15, whereby the film 11 is separated easily from the container and theupper surface of the container can be opened without damaging thecontainer.

[0057] One concrete example is as follows. As the container 10 there isused, for example, a tray 200 mm by 100 mm and 25 mm high and having afitting edge 15, or a tray having an upwardly expanded opening, or a cupor the like having an upwardly expanded opening 16 and having a diameterof 100 mm and a height of 70 mm. For example, in the case of a tray 200mm by 100 mm and 25 mm high and having a fitting edge 15, there is used,as the film 11 to be applied over the container 10, a film of a softpolyvinyl chloride having a melting temperature of 120° C., a stretchratio of 3.0, a thickness of 30 μm, which film has been cut to a sizelarge enough for the film to overhang from the container 10, forexample, a size of 220 mm×120 mm for a tray of 200 mm by 100 mm and 25mm high and having a fitting edge 15. For a cup having an upwardlyexpanded opening 16 and having a diameter of 100 mm and a height of 70mm there is used a film of a soft polyvinyl chloride which has been cutto a diameter of 120 mm.

[0058] Although in the above embodiment the shape of the containeropening is upwardly expanded as a whole, for another embodiment, whenthe present invention is applied to such a container as shown in FIGS.19 and 20 wherein an opening of the container, denoted as 1 in FIGS. 19and 20, is formed with an edge portion, denoted as 2 in FIGS. 19 and 20,projecting laterally outwards, film is sure to be fitted with theprojecting edge portion denoted as 2 in FIGS. 19 and 20, so that a solidedge portion of the film can be formed more positively and it ispossible to enhance the sealing performance.

[0059] For another embodiment of the present invention, as the film 11there also may be used a polyethylene stretch film having a melttemperature of 100° to 150° C., a stretch ratio of 3 to 10, and athickness of 11 μm to 40 μm, or a biaxially stretchable, multi-layerstretch film formed of an ethylene/vinyl acetate copolymer and a softpolyolefin resin.

[0060] For another embodiment of the present invention, as means forheating end portions of the film 11, the hot air blowers 13 may bereplaced by electric heaters or heating rollers.

[0061] Although in the above embodiment end portions of the film areallowed to converge by heating to form the solid edge portion, means forshrinking end of the film 11 is not limited merely heating means. Foranother embodiment of the present invention, as means for shrinking endportions of the film 11, acid or the like may be applied to end of thefilm 11 for shrinking and converging end of the film 11. This is usefulin case heating means gives harmful influence to the film 11. Appliedacid should be eliminated by cleaning or the like if necessary.

Second Embodiment

[0062] Another method for pulling a film which covers a containeraccording to the present invention will now be described with referenceto FIGS. 9 to 11. What is illustrated in FIG. 9 is a packaging apparatus103 provided with a packaging unit 102 for stretching a film 101. Thepackaging apparatus 103 comprises a container feed unit 104 and acontainer discharge unit 105 disposed on the left and right sides,respectively, of the packaging unit 102 and a film loading unit 106disposed behind the packaging unit 102. According to this arrangement, alarge number of articles to be packaged can be packaged in a continuousmanner. The container feed unit 104 feeds containers 107 to thepackaging unit 102 continuously one by one, the container discharge unit105 discharges a packaged container 108, and the film loading unit 106feeds the film 101 to the packaging unit 102 in a successive manner. Asto detailed structures of the container feed unit 104 and the containerdischarge unit 105, explanations thereof are here omitted.

[0063] The packaging unit 102 comprises a container carrier 109 whichincludes a container raising/lowering mechanism (not shown) for movingthe container 107 up and down while carrying it thereon, film drawers110, as a film grippers, for drawing out the film 101 to the packagingunit 102 and gripping four corners of the film, the film drawers 110being also used for stretching, film pulling mechanisms 111, as the filmgripper, and linear-acting actuators 112. The film pulling mechanisms111 themselves, which are provided four, can move back and forth andturn vertically and the film pulling mechanisms 111 located on thelinear-acting actuators 112 which are disposed two at right and leftpositions can also move in the longitudinal direction of the packagingapparatus 103, whereby a cut film 101 can be gripped, stretched andungripped.

[0064] On the other hand, the film 101, typical of which is a rollstretch film for food packaging, is inserted into the film loading unit106 at a predetermined position. A front end portion of the film 101 isfed to a film delivery section 113. In this case, a control is made sothat the front end portion of the film is set at an initial position atwhich it slightly overhangs to the packaging unit 102 side with respectto the film delivery section 113.

[0065] In such a configuration, when the container 107 charged with anarticle (not shown) has been fed onto the container carrier 109 in thepackaging unit 102, the linear-acting actuator 112 operates and two filmdrawers 110 located on the linear-acting actuators 112 and on the frontside of the apparatus grip the film 101 overhanging from the filmdelivery section 113, then the film 101 is drawn out to above thecontainer 107. Thereafter, two film drawers 110 located at rearpositions grip the film 101. The amount of the film 101 to be drawn outdiffers depending on the size of the container 107 and a control unit201 described below controls the film drawing-out operation (refer FIG.17). At this time, the film pulling mechanisms 111 not concerned indrawing out the film 101 are located at positions not obstructing thedrawing-out operation.

[0066] After the film 101 has been drawn out to above the container 107,the film pulling mechanisms 111 grasp the centers in each side of thefilm 101, both film pulling mechanisms 111 and film drawers 110stretches the cut film 101. More specifically, the film 101 is cut witha cutter (not shown) while both film pulling mechanisms 111 and filmdrawers 110 grasp the film 101. As a result, as shown in FIG. 9, thefour corners of the cut film 101, which is rectangular, are grasped bythe film drawers 110 and a central portion of the film is grasped atfour points by the film pulling mechanisms 111. For stretching the cutfilm 101 from the central portion of the film, as shown in FIG. 10, thefilm pulling mechanisms 111 move outwards crosswise from the centralportion of the cut film 101, while the film drawers 110 move in diagonaldirections. As a result, the cut film 101 whose central portion and fourcorners are thus grasped at eight points can be stretched by beingpulled from its central portion. The pulling operation is performed byactuators provided in the film pulling mechanisms 111 and the filmdrawers 110, but conditions such as pulling speed and pulling quantitydiffer depending on the properties of the film 101 and the specificationof actuators.

[0067] It is also possible to provide rotating mechanisms in the cutfilm grasping portions of both film pulling mechanisms 111 and filmdrawers 110 and effect film stretching through the rotating mechanisms.To be more specific, by grasping the cut film 101 at eight pointsthrough the film pulling mechanisms 111 and the film drawers 110 andcausing the film grasping portions of the actuators to turn downward asshowing in FIG. 11, a frictional force developed between the cut film101 and the film grasping portions becomes larger, so that the cut film101 can be grasped more firmly. Then, the film pulling mechanisms 111applies an outward pulling force to the film crosswise from the centralportion of the film, whereby the film is pulled from its central portionand is stretched thereby.

[0068] After the film 101 grasped at its four corners has thus beenstretched by being pulled from its central portion through the filmpulling mechanisms 111, the stretched film 101 is applied over thecontainer 107 and is made integral with the container, whereby there isformed a packaged container 108, in which the stretched film 101constitutes a cover portion as is the case with the description of thefirst embodiment. The process for forming the cover portion of thepackaged container 108 is as follows.

[0069] First, when such a state as shown in FIG. 10 has been attained,the container raising/lowering mechanism of the container carrier 109causes the container 107 charged with the to-be-packaged article to risetoward the stretched film 101. It is preferable that the rising speed be50 mm or so per second.

[0070] Upon contact of the to-be-packaged article or a container opening121 with the stretched film 101, the rising speed is decreased to 20 mmor so per second to cover the container opening 121 little by little.The container opening 121 is a fitting edge. Further, as shown in FIG.10, the stretched film 101 is pushed upward with the pressure of thecontainer 107 of the to-be-packaged article and the film drawers 110 andthe film pulling mechanisms 111 turn slightly, causing the overhangingportions of the film 101 overhanging from the container opening 121 toapproach the side faces of the container 107. At this time it ispreferable that the film grasping direction of the film drawers 110 andfilm pulling mechanisms 111 is upward toward the container opening 121(refer FIG. 4 for First Embodiment).

[0071] When end portions of the stretched film 101 have arrived at aposition lower than the container opening 121, as shown in FIG. 10,blowers 999 positioned within the packaging unit 102 are driven to blowhot air to the four sides of the container 107, thereby allowing thestretched film 101 to be fitted with the container opening 121, wherebya solid edge portion is formed and it is possible to form a packagedcontainer 108.

[0072] Also in the case where the grasping portions for the cut film 101by the film pulling mechanisms 111 and the film drawers 110 shown inFIG. 11 are each provided with a rotating mechanism, it is possible toform such a solid edge portion.

[0073] Although in the above embodiment end portions of the film areallowed to converge by heating to form the solid edge portion, means forshrinking end of the film 101 is not limited merely heating means. Foranother embodiment of the present invention, as means for shrinking endportions of the film 101, acid or the like may be applied to end of thefilm 101 for shrinking and converging end of the film 101. This isuseful in case heating means gives harmful influence to the film 101.Applied acid should be eliminated by cleaning or the like if necessary.

Third Embodiment

[0074] A further pulling method will now be described with reference toFIGS. 12 to 16. The same parts as those in the second embodiment aredesignated by the same reference numerals, and are not again explainedherein.

[0075] In the pulling method of the second embodiment the cut film 101was stretched by pulling with the film drawers 110 as well as the filmpulling mechanisms 111. On the other hand, in the pulling method aboutto be described below, there is used such a film stretching mechanism115 as shown in FIGS. 12 to 16 as a mechanism which applies an outwardpush-out force to the cut film 101 from the central portion of the filmto stretch the film.

[0076] The film stretching mechanism 115 is composed of a base 116 thatis capable of rising and lowering, and four arms 117 provided on thebase 116 and is positioned above the container carrier 109. The arms 117are each composed of an upper arm 118, a lower arm 119, and fingers 120.The film stretching mechanism 115 is a multi-joint robot adapted toperform a straight movement according to the rising and lowering of thebase 116 and rotation in the vertical direction and impart a swingmotion to the upper and lower arms 118, 119.

[0077] In such a configuration there are performed a pre-stretching stepusing film drawers 110 and a stretching step of expanding the cut film101 outwards from a central portion of the film with use of the filmstretching mechanism 115.

[0078] In the same manner as in the preceding pulling method the film101 which has been cut with a cutter (not shown) is grasped by filmdrawers 110. In this case, as shown in FIG. 13, after the four cornersof the cut film 101 have been grasped, the film is subjected to thepre-stretching step. In the pre-stretching step, the film 101, which isthus grasped at its four corners, is stretched in its diagonaldirections. More specifically, the film 101 gasped at its four cornersis stretched until the area thereof becomes 1.1 to 1.2 times the initialarea thereof. At this time the film 101 is wrinkle-free and is deformedelastically. If the film 101 is stretched to a greater extent at thestage of pre-stretching, a large pulling force is exerted in onlydiagonal directions, so that only the grasped four corners of the filmare stretched rapidly, which causes tear of the film.

[0079] After completion of the pre-stretching step there is performedthe stretching step in which the four-corner grasped film 101, which hasbeen stretched to 1.1 to 1.2 times, is expanded from its central portionoutwards in directions perpendicular to the four sides of the containeropening 121. First, as shown in FIG. 14, the film stretching mechanism115 moves down from above the four-corner grasped film 101 in such amanner that the four sides of the container opening 121 are in aone-to-one relation to the fingers 120 of the film stretching mechanism115. Since in this embodiment a tray having a generally rectangularcontainer opening 121 is used as the container 107, four fingers 120 areneeded in the film stretching mechanism 115. As the film stretchingmechanism 115 moves down, the fingers 120 apply pressure perpendicularlyto the four-corner grasped film 101, with the result that the fingers120 sink to the film. At this time, a perpendicular pressure exerted onthe film is about 90 to 170 kPa.

[0080] Next, the stretching step is carried out, in which thefour-corner grasped film 101 is expanded from its central portionoutwards in directions perpendicular to the four sides of the containeropening 121. This is attained by operation of the arms 117.

[0081] The upper and lower arms 118, 119 of the four arms 117 in thefilm stretching mechanism 115 are turned in directions perpendicular tothe four sides of the container 107, causing a frictional force and anadhesive force to be developed in an interface between the fingers 120of the film stretching mechanism 115 and the four-corner grasped film101 and thereby expanding the film 101. At this time the film 101 can bestretched horizontally by controlling the upper and lower arms 118, 119of the arms 117. If the amount of turn of the arms 117 is furtherincreased, the film 101 undergoes a plastic deformation. For stretchingthe film 101 in conformity with the size of the container opening 121 itis necessary that the amount of turn of the upper and lower arms 118,119 in the film stretching mechanism 115 be controlled in conformitywith the size of the container 107, as shown in FIG. 15. In this stage,fingers 120 provided in the film stretching mechanism 115 are caught atside portions of the film 101 without slipping off. This is because film101 winds in the fingers 120 according to the stretching of the film101.

[0082] While the film is stretched by the film stretching mechanism 115,the film 101 is held at the four corners thereof by the film drawers 110and its central portion is in a stretched state outwards under theaction of the arms 117. The amount of stretch of the film 101 stretchedby the film stretching mechanism 115 is such that the area of thestretched film is about 1.8 times the original area of the film, inwhich condition there is obtained a wrinkle-free, lustrous condition. Ifthe area is made larger, the film becomes easier to tear, so it ispreferable that the film be stretched to an area of 1.5 to 2 times theoriginal area.

[0083] Concrete conditions are as follows. Supposed that it is used aplastic tray having a container opening 121 of 150 mm×230 mm and 30 mmhigh. In this case, a roll stretch film constituted by a biaxiallystretchable, multi-layer polyethylene film having a commercial size of250 mm wide by 10˜20 μm thick is used as film 101. The film 101 is cutto a 250 mm square with a cutter, which cut film is then subjected topre-stretching up to a size of about 260 mm×260 mm. In this case, caremust be exercised so that the film is not brought into contact with thecontainer 107 and the upper and lower arms 118, 119 and fingers 120 asconstituents of the film stretching mechanism 115 at least in thepre-stretching stage because the stretch film itself becomes very stickyand would adhere to them due to its adherence.

[0084] After the end of pre-stretching, the fingers 120 of the filmstretching mechanism 115 move down toward the four-corner grasped film101 and sink to the film. At the end of the fingers 120 there areprovided a material having characteristics in which causes friction morethan certain value to the film 101. It is preferable used fiberstructured material having Netting formation mingled with innumerablefibers for the material, e.g., leathers (including both genuine leathersand artificial leathers like vinyl leathers, synthesis leathers, or thelike), non-woven fabric, and cellular urethane sponge rubber havingclosed cell or continuous cell. These materials have moisture-absorbedcharacteristics, so that friction power thereof does not decrease underhigh damp atmosphere. Thus, film 101 can be used easily by using abovematerial in the fingers 120.

[0085] After pre-stretching by the film drawers 110 and after stretchingof the four-corner grasped film 101 from inside to the outside by thefilm stretching mechanism 115, the stretched film is united with thecontainer 107 charged with an article to be packaged to form a packagedcontainer 108, in which the stretched film 101 constitutes a coverportion as is the case with the description of the first embodiment. Theprocess for forming the cover portion of the packaged container 108 isas follows.

[0086] First, a container raising/lowering mechanism of a containercarrier 109 causes the container 107 to rise toward the stretched film101 at a speed of 50 mm or so per second. After a portion of thecontainer 107 comes into contact with the stretched film 101, the filmis pushed upward at a rate of 20 mm or so per second by the pressure ofthe container 107 or of the to-be-packaged article, so that the filmdrawers 110 turn slightly. The film drawers 110 cause overhangingportions of the stretched film 101 overhanging from the containeropening 121 to approach the side faces of the container 107. At thistime the film grasping direction of each film drawer 110 is preferablyupward toward the container opening 121. By so doing, front ends of thefilm drawers 110 are positioned below the container opening 121.

[0087] On the other hand, the fingers 120 of the film stretchingmechanism 115 are at this time positioned outside the four sides of thecontainer 107 as in FIG. 15. In this state, blowers 999 positionedwithin a packaging unit 102 as in FIG. 16 are driven to blow hot airagainst the four sides of the container 107 to form a solid edgeportion, allowing the stretched film 101 to be fitted with the containeropening 121, whereby a packaged container 108 can be formed.

[0088] By stretching the film 101 outward from its central portion inaccordance with the above pulling method it becomes possible to stretchthe entire film 101 uniformly along the container edge and the formationof a solid edge portion can be done positively. Besides, since thecentral portion of the film 101 is stretched or expanded outwards andthe film 101 is thereby stretched uniformly, wrinkling of the film 101caused by a returning force in the container opening 121 at the time offormation of the packaged container 108 is suppressed and the container107 is prevented from being deformed. Further, since the film expandingdirections are perpendicular to the sides of the container 107, it ispossible to stretch the film 101 in conformity with the shape of thecontainer 107 used.

[0089] Although in the above embodiment end portions of the film areallowed to converge by heating to form the solid edge portion, means forshrinking end of the film 101 is not limited merely heating means. Foranother embodiment of the present invention, as means for shrinking endportions of the film 101, acid or the like may be applied to end of thefilm 101 for shrinking and converging end of the film 101. This isuseful in case heating means gives harmful influence to the film 101.Applied acid should be eliminated by cleaning or the like if necessary.

[0090] FIGS. 17 is a block diagram of an operating mechanism used inthis packaging apparatus 103 introduced in the second embodiment andthird embodiment. Although same structured-operating mechanismillustrated in FIG. 17 also controls the packaging apparatus 5introduced in the first embodiment, details thereof are eliminated.

[0091] A control unit 201 as a controller is microcomputer consist ofCPU, RAM and ROM. The control unit 201 controls peripheral portions orunits by calculating operation of the CPU according to operating systemsand operating program stored in a data storage apparatus. It is used,for instance, ROM, Hard disk, or optical information recorded media likeMO, DVD-ROM, DVD-RAM, as the data storage apparatus. The recorded datain the hard disk, MO, DVD-ROM and DVD-RAM can be read by a data readableapparatus, such as HDD, MO driver, DVD driver or the like, connectedwith CPU. The peripheral portions or units are controlled so as tooperate preferable by control of the control unit 201 according to theoperating program stored in the data storage unit, thereby operation ofthe controller is executed.

[0092] Under control of the control unit 201, initial conditions are setfrom an operating conditions input device 202, and upon detection of acontainer 107 by a container sensor 203 there is started a packagingoperation. The sensing operation of the container sensor 203 and that ofa counter circuit 204 cover a container feed mechanism 205 and acontainer discharge mechanism 206, and a comparison is made between apreset number of packaged containers 108, which is inputted by theoperating conditions input device 202, and the present packaging state.Processing (packaging operation) is continued until the preset number ofpackaged containers 108 is reached. Further, in the same figure, thereappears a film actuator 207 as a generic term for film grasping,drawing-out and stretching actuators, and a film feed mechanism 208controls the amount of film 101 to be drawn out with operation of thefilm actuator 207. A container raising/lowering mechanism 209 causes toelevate the container carrier 109. The actuator of the containerraising/lowering mechanism 209 that is controlled by the control unit201 attains the rising and lowering of the container carrier 109. Theblower 999 (blower heater 999) is also connected with the control unit201 and is controlled by the control unit 201.

[0093]FIG. 18 is a flow chart showing an outline of a packagingprocedure used in the packaging apparatus 103. The packaging operationwill now be described on the basis of this flow chart.

[0094] First, the control unit 201 executes initializing processaccording to an initial values input by the operating conditions inputdevice 202 (step S1). As initial values, an operator inputs the size(type) of the container 107 and a preset number of packaged containers108. The film 101 inserted in the film loading unit 106 differs in itscut area depending on the size of the container opening 121, so once thesize (type) of the container 107 is inputted, the area of the film 101to be cut is determined unconditionally.

[0095] After the input of initial values the operator puts the container107 on the container carrier 109 disposed in the container feed unit104. In this stage, the control unit 201 detects whether the container107 is present or not on the container carrier 109 in the container feedunit 104 by the container sensor 203 (step S2). That is, whether thecontainer is present or not is checked by the container sensor 203 as alimit switch, an image sensor, or a pressure sensor.

[0096] When the feed of the container 107 onto the container carrier 109has been detected, the control unit 201 controls the container feedmechanism 205, so that the container 107 is fed into the packing unit102 by the container feed mechanism 205 (step S3). After this process,packing operation of the container 107 is performed by a containerraising/lowering mechanism 209 and the film actuator 207. In the firsthalf of the packaging operation the film 101 is subjected to a series ofsuch operations as drawing-out, grasping (step S4), cutting and pullingand is stretched thereby (step S5). In the latter half of the packagingoperation, which operation is for forming a solid edge portion, thecontainer opening 121 is covered with film 101, hot air is blown againstend portions of the film 101, and the grippers of the film drawers 110and the film pulling mechanism 111 are deactuated. In this case, thefilm 101 is drawn near the container opening 121 and hot air is jettedby the blowers 999. The film 101 shrinks during the lapse of a hot airjet time of about 3 seconds and the film 101 is ungrasped in synchronismtherewith (step S6). As a result of this operation, film 101 isconverged around the edge of the container 107, so that the film 101covers the container opening 121.

[0097] The packaged container 108 thus obtained is fed from thepackaging unit 102 to the container discharge unit 105 by the containerdischarge mechanism 206 (step S7) and is counted by a counter circuit204 (step S8). The above flow is repeated until the initially set numberof packaged containers is reached (step S9). Immediately after thedischarge of one packaged container 108 the next container 107 isdetected.

[0098] Although the packaging apparatus 5 introduced in the firstembodiment of the present invention is also controlled by same processdescribed in the flow chart showing in FIG. 18, the details thereof iseliminated.

[0099] The present invention may be embodied in other specific formswithout departing from the spirit or essential characteristics thereof.The present embodiment is therefore to be considered in all respects asillustrative and not restrictive, the scope of the present inventionbeing indicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

[0100] The present application is based on Japanese Priority DocumentHei 11-18503 filed on Jan. 27, 1999 and Hei 11-369376 filed on Dec. 27,1999 the content of which are incorporated herein by reference.

What is claimed is:
 1. A packaging container, comprising: a containerfor accommodating an article to be packaged, the container having aperipheral fitting edge and an upper opening; and a cover member formedby a film for covering the opening of the container, end portions of thefilm being converged to form a solid edge portion for fitting with thefitting edge of the container.
 2. A packaging container according toclaim 1, wherein the fitting edge of the container is formed so as toproject laterally outwards.
 3. A packaging container according to claim1, wherein the opening of the container is formed in a shape whichexpands upwards of the container, and the edge of the container openingis formed as the fitting edge.
 4. A packaging container according toclaim 1, wherein the film is a stretch film.
 5. A packaging method,comprising the steps of: covering an opening of a container foraccommodating an article to be packaged is covered with a film of a sizewhich permits the film to overhang sideways from the opening of thecontainer; and converging the overhanging portions of the filmoverhanging sideways from the container opening to form a solid edgeportion of a high rigidity for fitting with a fitting edge formed on thecontainer side.
 6. A packaging method, comprising the steps of:stretching a central portion of a film for covering an opening of acontainer which accommodates an article to be packaged outwards of thefilm so as to afford a film size overhanging sideways from the openingof the container; covering the opening of the container with thestretched film; and converging overhanging portions of the filmoverhanging from the container opening to form a solid edge portion forfitting with a fitting edge formed on the container side, the solid edgeportion having a higher rigidity than the rigidity of the film.
 7. Apackaging method according to claim 6, wherein the central portion ofthe film is stretched outwards of the film and in directionsperpendicular to sides of the container.
 8. A packaging method accordingto claim 6 or 7, wherein a central portion of the film is allowed tostretch outwards of the film by straight movement of film grippers thatgrasps the film.
 9. A packaging method according to claim 6 or 7,wherein a central portion of the film is allowed to stretch outwards ofthe film by rotating movement of film grippers that grasps the film. 10.A packaging method according to claim 6 or 7, wherein a central portionof the film is allowed to stretch outwards of the film by the stepsincluding: grasping the film by film grippers; sinking a plurality offingers that is capable of spreading; and spreading the fingers so as tostretch outwards of the film.
 11. A packaging method according to claims5, 6, 7, 8, 9 or 10, wherein end portions of the film are allowed toconverge by heating to form the solid edge portion.
 12. A packingapparatus, comprising: a controller for controlling each portion so asto allow execution of certain operation; a film grippers, controlled bythe controller, for grasping a film afforded a film size overhangingsideways from the opening of the container which accommodates an articleto be packaged, the film grippers positioning the film above thecontainer opening; a mechanism, controlled by the controller, for movingthe film grasped by the film grippers to the container openingrelatively so as to cover the container opening with the film; and amechanism, controlled by the controller, for converging the overhangingportions of the film overhanging sideways from the container opening toform a solid edge portion of a high rigidity for fitting with a fittingedge formed on the container side.
 13. A packaging apparatus accordingto claims 12, wherein the film grippers grasp four corners of the filmand stretch the film outwards of the film.
 14. A packaging apparatusaccording to claims 13, further comprising a film pulling mechanism,controlled by the controller, that grasps each sides between the cornersof the film and stretch the film outwards of the film.
 15. A packagingapparatus according to claims 12, further comprising a plurality offingers, controlled by the controller, that is capable of spreading andspread so as to stretch outwards of the film.
 16. A packaging apparatusaccording to claims 12, 13, 14 or 15, wherein the mechanism forconverging the film converges by heating the edge of the film to formthe solid edge portion.
 17. A packaging apparatus according to claims12, 13, 14, 15 or 16, further comprising a film unit for cutting thefilm so as to afford a film size overhanging sideways from the openingof the container.